1. Field of the Invention
This invention relates to an electromagnetic wave matching element adapted for converting electromagnetic waves outputted from a gyrotron equipment to transmit them to a transmission system such as corrugated waveguide, etc.
2. Description of the Prior Art
At present, systems using electromagnetic waves are being studied in order to heat plasma in a nuclear fusion reactor. As a large power high frequency oscillating source of the millimeter wave band, high order mode gyrotron equipments are considered to be promising candidates, and are on the way to development. Generally, the gyrotron equipment accelerates and rotates thermions (thermoelectrons) generated at a cathode portion of an electron gun in the electromagnetic field to allow a portion of the rotation energy of the electrons to resonate in a cavity resonator to thereby convert it into electromagnetic wave energy. This electromagnetic wave (chiefly millimeter wave) is converted into electromagnetic wave beams by a mode converter and a mirror system having a plurality of mirrors to output them to an external location.
In the gyrotron having output of MW class, there is a problem in that when millimeter waves are passed through an output window made up of a dielectric body, a rise in temperature by heating of the dielectric body takes place so that the output window may be damaged. In order to suppress rising in temperature of the output window composed of a dielectric body, there have been proposed an approach in which mode converter and the mirror system are used to split millimeter waves oscillated at the cavity resonator into plural millimeter wave beams to take out them from plural output windows, and the like.
The millimeter wave beams outputted from the gyrotron are ordinarily transmitted up to the nuclear fusion reactor through a transmission system such as corrugate (corrugated) waveguide, etc. In the case where millimeter wave beams are taken out from plural output windows, one transmission system is required with respect to one output beam. Accordingly, the necessity of preparing plural transmission systems with respect to the single gyrotron having plural outputs takes place.
When a gyrotron having plural outputs is made up in order to suppress breakage of the output window as stated above, the necessity of installing plural transmission systems with respect to a single gyrotron takes place, with the result that the manufacturing cost of the transmission system becomes extremely large.